Page 7 - Sea-level change_2004

ARTICLE IN PRESS
K. Lambeck, A. Purcell / Quaternary Science Reviews 24 (2005) 1969–1988 1975

Fig. 2. (a,b) Hydro-isostatic contributions Dz I h at 12 ka BP corresponding to the decay of the global ice sheets with cessation of melting at
6.8 ka BP. (a) The first-iteration solution of the sea-level equation in which the water loadis representedby a globally uniform water loadequal to the
equivalent sea-level for the epoch. (b) The fifth-iteration solution of the sea-level equation in which the coupling between the various terms is fully
incorporatedandthe water-load definition is gravitationally consistent with the potential of the earth–ocean–ice system andwith the shoreline and
ice-grounding lines for the epoch. (c) Same as (b) but at 6 ka BP. (d–f) The total predicted relative sea-level change at 20, 12 and 6 ka BP, respectively,
for the nominal earth and ice model, including Dz I g and Dz I h . The contour notation is the same as in Fig. 1.

shown: the first is for the first-iteration solution of the change here will, by analogy of loading of an infinite
sea-level equation in which the water loadaddedinto elastic layer over a fluidby a semi-infinite slab load, be
the global oceans is representedby a slab of uniform approximately 50%, or about 20–25 m, across the
thickness equal to the change in esl. In the local isostatic coastal zone. From Fig. 1e, the water loadfor the
limit, the sea-floor subsidence would be ðr = Mediterranean basin is greater than the esl value for this
ice
r Þ Dz esl or 15 m at 12 ka BP. In the same limit, epoch by between 10% and 20% andthe actual
mantle
the displaced mantle material uplifts the non-loaded water-loadmagnitude will exceedthat for this simple esl
continents by a maximum of about twice this amount slab model. Thus the fully coupled models will be
(ocean/landarea E 2) andthe relative sea-level change required(Figs. 2b andc) andthese modify the first
at the crustally-shearedcoast lines (of a local isostatic iteration result in two important ways: (i) some of the
model) would be 45 m. The local isostatic state would water-loaddisplacedmantle material will compensate
not be reachedat the ocean–landboundaries unless the for the reboundbeneath the ice-loaded areas, and (ii) the
lithosphere failedandthe maximum relative sea-level thickness of the water column is modified by the glacio-